3 notes above! :)

I saw this group of birds circling and cruising on the thermals as they slowly passed over the property. I heard them cawing and doing aerobatics, tumbling and doing somersaults and generally having a wonderful time!

After reading the information below and reading more on the web about the differences between these birds, I am not sure. The fan-shaped tails and the fact they are in a flock suggest they are crows, but crows have more of a flat wedge of their tail, so...this suggests these birds are ravens. Here's a picture to compare: Raven vs. crow tail feathers The aerobatics and low cawing sounds suggest they are ravens. They were quite large, which says raven; crows are a LOT smaller, and these guys were definitely big. If I'd been closer I'd be able to see their faces, which would tell me for sure. Judging on the extra information from Leapfrog (Art), I'm thinking they are ravens (my original feeling)....what do you think? Here's more info though, very interesting! :D

How to Tell a Raven From a Crow, a helpful guide from Audobon!
These black birds may look similar in some ways, but several distinctive traits help set them apart.

These two species, common ravens and American crows, overlap widely throughout North America, and they look quite similar. But with a bit of practice, you can tell them apart.

Ravens are larger, the size of a red-tailed hawk. Ravens often travel in pairs, while crows are seen in larger groups. (In flight, ravens will soar and do somersaults on thermal or wind-generated updrafts, but crows do not soar. So if that big black bird is soaring, it's a raven.) Also, watch the bird's tail as it flies overhead. The crow's tail feathers are basically the same length, so when the bird spreads its tail, it opens like a fan. Ravens, however, have longer middle feathers in their tails, so their tail appears wedge-shaped when open. (but not flat along the bottom like a crow)

Listen closely to the birds' calls. Crows give a cawing sound. But ravens produce a lower croaking sound.

This is what a Common Raven sounds like and this is what an American Crow sounds like.